1) Field of the Invention
This invention has to do with electromagnetic vibratory drive units. More specifically, it has to do with drive units that are provided with removable side plates. These side plates are removed and replaced with other side plates either as a mass adjustment means or as a means to configure multiple vibratory drive units together in tandem or siamesed configurations. These drive unites are integral with vibratory feeders known as two mass feeders which are used extensively in the material handling equipment arena.
2) Description of Related Art
The prior art closest to this invention is represented by the applicant's assignee's own product line. Although vibratory feeders housing some of the features disclosed and discussed herein are available, the products of FMC Corporation, the assignee, are representative of the prior art. FMC Corporation's vibratory feeder model BF-2 shows the use of two drive units or vibratory exciters in driving a single product delivery trough. These drive units are mounted one behind the other under the trough of the feeder. They are independent units that are not connected together directly but rather are both attached to the bottom of the trough. This is an acceptable arrangement but is not an optimized embodiment. The difficulty is that the feeder trough has to be made very stiff and heavy in order to minimize its effect as a spring between the two vibratory drives. It is, the feeder trough, is not stiff enough the flexible trough will set up reasonances that prevent smooth product drive and flow of the product throughout the length of the trough.
The prior art vibratory feeder devices do not include the modular structure of this invention. The modular structure allows the feeder to be assembled from a fewer number of stock components for a range of machine capacities than would have been necessary if a similar range of machine capacities had to be made from non-modular assemblies. For example the range of mass of the second mass, the trough of the feeder and the feeder mounting brackets that the vibratory feeder can drive, subject to holding the stroke of the feeder trough in the range of 0.070" to 0.100" ins in the range of 20 lbs to 30 lbs. The modular unit hereof in the basic configuration, that is, with a single drive and what are termed "light side plates"--will have a range of 54 lbs to 84 lbs.
In related applications of vibratory electromechanical exciters wherein an exciter or drive unit is used to drive a feed conveyor, including a product delivery trough, it is known to use multiple drive units to drive a single trough. The trough referred to herein is a generally elongated channel open at a discharge end thereof. Its use, in a normal embodiment is to move product from a bin or hopper to a second processing station such as a packaging station. As these troughs can be quite long it has not been unusual to see two drive units, spaced apart and independent of each other attached to and driving such a single trough. This presents at least two problems. First, the trough itself has to be rigid enough to ensure that there is no untoward flexation of the trough between the two drive units. This means that the trough has to be massively reinforced and gusseted to control such flexure and supply the necessary rigidity. The extra mass of the now rigid conveyor requires a larger pair of drive units then would normally be needed if the trough were of the unenhanced configuration. A second problem, although this is a lesser problem, is that there may be a tuning problem between the two or more drives. This is not difficult to control or adjust for--particularly where the trough has been structurally enhanced--however, it has to be addressed.
Another problem with the known application of vibratory exciters is that since the mass relationship between the trough and the undriven structure of the feeder is crucial to good feeder performance, it has been important to have, as a manufacturer, a wide range of masses of feeder drives to accommodate a wide range of trough masses. This is detrimental as it requires an inventory of many feeder drives and doesn't provide economies of scale conducive to good cost control measures.
It has been the practice in the industry to add mass to a two mass system to arrive at a desired ration between the first mass and the second mass of a system. This desired ratio is seldom a one-to-one ratio but is usually a ratio where the base mass on first mass is a multiple of the second mass. For instance, if the second mass weighs twenty pounds the base mass may be sixty pounds. This would yield a three to one ratio of first mass--the drive mass--to the second mass--the driven mass which includes the trough or product delivery apparatus.